The present invention relates to a double-headed piston type swash plate compressor.
Japanese Laid-Open Patent Publication No. 2009-287465 describes an example of a double-headed piston type swash plate compressor. The compressor of the publication is provided with a housing including a front cylinder block, a rear cylinder block, a front housing joined with the front cylinder block, and a rear housing joined with the rear cylinder block. A shaft bore (rotation shaft accommodation bore) extends through each cylinder block, and a rotation shaft is inserted through the shaft bores. A lip seal type shaft sealing device is arranged between the front housing and the rotation shaft. The front housing includes an accommodation chamber (suction chamber) that accommodates the shaft sealing device.
A swash plate chamber is defined in the front and rear cylinder blocks. A swash plate is arranged in the swash plate chamber. The swash plate is fixed to and rotated integrally with the rotation shaft. The front cylinder block includes a plurality of cylinder bores arranged around the rotation shaft. The rear cylinder block also includes a plurality of cylinder bores arranged around the rotation shaft. The cylinder bores of the front cylinder block are aligned with the corresponding cylinder bores of the rear cylinder block. A double-headed piston is accommodated in and reciprocated in each pair of aligned cylinder bores. The front cylinder block includes an intake hole that opens toward the swash plate chamber.
A communication passage extends through the front housing and front cylinder block between adjacent cylinder bores. The communication passage includes an inlet that opens in the swash plate chamber and an outlet that opens in the accommodation chamber. Thus, the communication passage communicates the swash plate chamber and the accommodation chamber.
A plurality of slots (communication conduits) are formed in the front cylinder block around the shaft bore near the front housing. The slots are formed at equal intervals in the circumferential direction. Each slot communicates the accommodation chamber and the shaft bore. Further, the rotation shaft includes a groove passage, which is formed to constantly overlap at least one of the slots. The slots constantly communicate the accommodation chamber and the groove passage. Further, the front cylinder block includes a plurality of suction passages that communicate each of the cylinder bores with the shaft bore. The suction passages are arranged at equal intervals in the circumferential direction. Each suction passage includes an inlet, which opens to the shaft bore in correspondence with the groove passage, and an outlet, which opens toward a front compression chamber defined in a corresponding one of the cylinder bores. Each suction passage is inclined so that the inlet is located at the rear of the outlet.
Refrigerant is drawn into the swash plate chamber through the intake hole. The refrigerant then flows through the communication chamber into the accommodation chamber. The refrigerant in the accommodation chamber flows through the slots into the groove passage. Then, the refrigerant is drawn from the groove passage into each front compression chamber through the corresponding suction passage.
In the piston type swash plate compressor of the above publication, the groove passage communicates the slots and the inlets of the suction passages. However, the overlapping region of the groove passage and the slots is often narrower than the overlapping region of the groove passage and the inlets of the suction passages. This may result in an insufficient amount of refrigerant being drawn into each suction passage through the slots and groove passage.
Accordingly, the above publication discloses a tapered communication conduit formed in the front cylinder block and extending in the circumferential direction entirely around the shaft bore near the front housing. The overlapping region of the tapered communication conduit and the groove passage is greater than the overlapping region of the groove passage and the slots. This resolves the problem of an insufficient amount of refrigerant being drawn into each suction passage through the groove passage. However, the formation of the tapered communication conduit in the cylinder block decreases the bearing surface of the cylinder block in the shaft bore that receives the rotation shaft near the front housing. As a result, the rotation shaft is apt to tilting. This may cause friction between the rotation shaft and the surface defining the shaft bore thereby adversely affecting wear resistance of the rotation shaft and shaft bore.